The title is self-explanatory. There's a subreddit that is somewhat unpopular, and I want to post a billboard about it here.

looking at the rules pertaining to billboards, would probably be best to file a ticket to see if its staff approved

Information

All billboards must be approved by a staff member. This can take up to 24-48 hours.
Banner size is 480x90 and we accept jpg, png and gif formats.
We accept the following sites: Subeta pages, fansites, deviantart pages, etsy shops and youtube channels.
We accept other pages, but it's up to staff discretion to accept them. Keep it PG 13 and good natured.
We reserve the right to reject any ad, for any reason.
We will send you an event when your billboard runs out of impressions!

For a definitive answer, I'd file a ticket.